textproduct: Albany

WHAT HAS CHANGED

Ensemble guidance continues to favor an eastward-progressing trough that will bring rain showers to the region as early as Sunday afternoon through Monday. However, this trough now appears to potentially split into northern and southern portions which don't look to phase. This will ultimately impact the track of an associated surface low and the axis of heaviest rainfall which remains uncertain. Therefore, confidence in rainfall amounts and isolated threat of flash flooding has lowered.

KEY MESSAGES

1) There is a medium to high chance for widespread rain showers across the region Sunday afternoon through Monday afternoon.

2) There will be potential for isolated flash flooding, particularly Sunday night into Monday when the heaviest rain is expected to fall. Those areas most at risk for flash flooding will be those that received the most rainfall this past week.

DISCUSSION

KEY MESSAGE 1...

Latest ensembles continue to portray the eastward shift of a large-scale, mid- to upper-level, northern-stream trough Sunday into Monday that could bring our next best chance for widespread showers. However, the variation within the synoptic details of the projected solutions errs to the complexity of the incoming system and the subsequent uncertainty regarding not only the spatial extent of rain that we will receive, but the amounts.

As of this afternoon's update, ensembles seem to be in good agreement that the primary, mid- to upper-level trough will deepen through the Ohio and Tennessee River Valleys tomorrow into tomorrow night. Short- to medium- range, deterministic models take things a step further and indicate a deepening to the point of the development of a mid- level, closed low in the the Ohio Valley by tomorrow afternoon. As this system tracks eastward and begins to weaken tomorrow night, a secondary piece of the northern stream becomes disconnected from the primary trough due to the persistence and stall of the closed low. These two troughs largely don't appear to phase as they continue eastward towards the East Coast. But, in the outlying scenario where they do, we now have three scenarios that look to occur:

Scenario 1: Let this be the favored scenario wherein the two troughs do not phase and there are ultimately split axes of rainfall. In this case, an initial fluid moisture axis will move into the region Sunday afternoon, driving an area of showers for areas to the north and west of Albany. Then, as the two troughs begin to separate, the moisture axis becomes split between and northwesterly and southeasterly component, bringing a break in showers Sunday night. Ultimately, a primary moisture axis oriented southwest to northeast from the Gulf along the East Coast, will largely bypass us to the south, but allow showers to move back into areas south of Albany by early Monday morning. The secondary moisture axis will develop along the eastern Great Lakes where an area of low pressure will develop along a pseudo- stationary boundary, enhancing low- level convergence and moisture availability. Another batch of showers will therefore occur for areas to the north and west of Albany Monday morning before a surface wave glides along the northern fringe of the primary trough. This will allow potentially enhanced rainfall to encroach on the Mid-Hudson Valley and southwestern New England with lighter showers elsewhere. This would primarily drive isolated flash flooding concerns for portions of the Mid-Hudson Valley and southwest New England.

Scenario 2: Let this be the scenario wherein the two troughs do not phase, but the aforementioned surface wave stays to our south. In this case, the moisture axis would again be split as in the previous scenario, but this time, rainfall remains lighter given the better forcing and moisture passing by to our south. This would ultimately give us lighter rain across the region and make for very few, if any, flooding concerns.

Scenario 3: Let this be the outlying scenario wherein the two troughs phase. In this case, a fluid moisture axis will align from the Gulf into the Northeast along the East Coast. An area of low pressure at the surface will develop along a pseudo- stationary boundary oriented across the Eastern Great Lakes. An axis of heavier rainfall will subsequently develop within our area Sunday night into Monday morning, following scattered showers Sunday afternoon mainly north and west of Albany. This scenario would ultimately give us the most QPF, but heaviest amounts and locations of such would depend on the eventual orientation of the heavy rain axis. At this time, this scenario seems to drive isolated flash flooding concerns across the Capital Region where the axis of heaviest rain looks to set up.

They key take away here is that we are likely to see some rain across much of the region Sunday afternoon into Monday. The uncertainty is exactly how much and where those amounts will fall. These details will ultimately directly impact the overall concern and locations for concern of isolated flash flooding.

KEY MESSAGE 2...

After this week's historic rainfall, soils are, to no surprise, overly saturated. In fact, according to the NYS Mesonet soil moisture analysis, over half of our CWA is at 50-75%, if not greater, moisture capacity. According to the latest NAEFs, PWATs are expected to reach 1.5-1.75 by Monday which is 2 STDEVs above normal. Especially given the first and third scenarios, there is definitely potential for some heavier downpours Sunday night into Monday and, in particular, to places that saw heavy rainfall previously this week. Therefore, isolated to possibly even scattered flash flooding is probable. However, as previously stated, it is going to be highly dependent on the ultimate set up of the system. Currently, ensembles are projecting about a medium chance for at least 0.5" of rainfall from Sunday night through Monday. Latest 1 hr FFG indicates most of our area only needs 1-2" (if not less) for flash flooding to occur. What will help is two fairly dry days for the remainder of today and tomorrow. However, we will continue to monitor the situation closely and remain vigilant of any flooding concerns given the latest event.

AVIATION /19Z FRIDAY THROUGH WEDNESDAY/

Predominately VFR conditions are expected through this afternoon with SCT to BKN cumulus ranging from 3-5 kft. There will be a medium chance for any more robust showers to produce intermittent IFR conditions through 23Z. By 23 - 01 UTC, skies will clear and winds will become light/variable. This will support fog potentially redeveloping at all terminals tonight. Any fog that does develop should diminish by 12Z.

Outlook...

Saturday Night: No Operational Impact. NO SIG WX. Sunday: Low Operational Impact. Breezy. NO SIG WX. Sunday Night: High Operational Impact. Likely SHRA...TSRA. Monday: High Operational Impact. Definite SHRA...TSRA. Monday Night: Moderate Operational Impact. Chance of SHRA...TSRA. Tuesday: Moderate Operational Impact. Chance of SHRA...TSRA. Tuesday Night: Moderate Operational Impact. Chance of SHRA. Wednesday: Moderate Operational Impact. Chance of SHRA...TSRA.

ALY WATCHES/WARNINGS/ADVISORIES

CT...None. NY...None. MA...None. VT...None.